Action 6: Assessment of environmental pollution levels via compilation of a monitoring network for the identification of sampling sites based on hydrological, hydro-geological and morphological characteristics of the area
Action 6 dealt with the environmental monitoring of the pilot area of the EcoPest project, and with providing information about pollutant levels in the water bodies and in the soil, which come from human activities related to agriculture. These pollutants include firstly residual concentrations of pesticides, and secondly, concentrations of fertilizers. The Action focused on those changes clearly connected with agricultural activities, especially regarding the use of fertilizers, and so was concerned with assessing nitrogen compounds (NO3, NH4+). Furthermore, in order to gain an integrated view of the environmental quality, the following parameters were determined: Ca2+, Mg2+, SO42-, Cl-, HCO3-, CO32-, Fe, Zn, Mn, and Ni. The levels of these ions and elements are primarily related to the geological substrate, and their changes are mainly the result of physical processes (see also Action 2). Nonetheless, the EcoPest team considered it worthwhile to monitor them, and building up as detailed an understanding as possible of the chemical interactions within the pilot area. Levels of heavy metals, such as Pb, Cu and Cd, were also analytically measured.
In the same samples, toxicity bioassays were conducted on indicator organisms for environmental quality. These are aquatic organisms belonging to various taxonomic classes, and soil organisms.
A monitoring network was established though which water samples were collected from wells, boreholes, surface water from the river and the unsaturated zone. These give indications of pesticide leakage from the plant-soil system within the pilot area. However, it ought to be underlined that the approach to planning and operation of the monitoring network had two aims. Not only is the network intended to record and document the immediate or direct responses of the system to the agricultural activities, but is also undertaken with a view to a long-term survey - the ultimate objective being to extend and continue the Project after its completion, thus prolonging the environmental benefits in the future.
Sampling was carried out at specific time periods during 2009, 2010, and 2011 – these last two years being those which saw the application of the reduced pesticide input systems. Apart from the evaluation of the absolute values of pollutant levels in the environmental samples, these years’ results are comparable to the respective ones being detected during Action 2, from which the current environmental state was estimated. Through this comparison it will be possible to produce the first indications of the effectiveness of the low-input pesticide systems, and the rational use of pesticides in cotton, maize and tomato crops.
Regarding the evaluation of the estimated inorganic pollutants’ levels, it should be mentioned that before 2009, due to long-lasting problems of high nitrates levels in the area, part of the broader pilot area was registered in the National Nitrogen-Pollution Reduction Program. Consequently, any changes in the concentration of the nitrate and ammonium ions are not expected to be significant in the quantitative properties of the applied fertilization, at least for the farmers who are participating in this project.
As for the rest of the systems investigated in the Project, the surface water is a dynamic system and the low number of sampling sites makes assessment of changes only indicative. The same applies for the karst aquifer. In any case, this aquifer would not be affected during the time schedule of the project, as the introduction of a potential pollutant from the surface would not be immediate. Therefore, for the time period 2010-2011, the monitoring network focused mainly on the alluvial aquifer and the unsaturated zone. The alluvial aquifer remains in an intermediate state, as the immediacy of any influence depends on various factors, such as the level of the aquifer, the thickness of the unsaturated zone, the nature of the formations, the effect from zones outside the Project’s control, etc. Finally, in the soil, there were no measurable changes for the inorganic pollutants. This was because there were no significant changes in the levels of fertilization; in most cases inputs were already reduced, due to the concurrently operating Nitrogen-Pollution Reduction Program.
Regarding the inorganic pollutants, the Action was concerned with changes due to reasons clearly connected with agricultural activities, thus was focused on nitrogen compounds (NO3, NH4+). The results for the unsaturated zone revealed an average annual reduction of 52.6 % in ΝΟ3- concentrations. In the case of the ammonium ions a reduction in concentration was recorded in 10 out of 13 sites, with an average annual reduction of 73.2 %.
The parameters Ca2+, Mg2+, SO42-, Cl-, HCO3-, CO32-, Fe, Zn, Mn, Ni are mainly related to the geological substrate and their changes are primarily caused by physical/natural processes. No correlation was found between the previously mentioned heavy metals and the pesticides used in the pilot area (see also Action 2).
While parameters Pb, Cu and Cd, are related to agricultural activities - either as pesticide additives (Pb and Cu in copper-chemicals) or as additives in fertilizers (Cd in phosphate-fertilizers), they were not assessed because copper-chemicals were not found to be widely applied in the pilot area. Furthermore, the Cd concentrations were so low that any reliable change could not be quantified.
The problem of water and soil pollution in the pilot area due to pesticide residues is focused on herbicides (mainly glyphosate, fluometuron, ethalfluralin, terbuthylazine and s-metolachlor). The occurrence of these is expected, due to the large number of hard-to-kill perennial weeds (Actions 2 & 3).
Regarding the levels of residual pesticides in the environmental samples, the following results were observed:
The total average of all pollutants in wells was reduced by 38% in 2010 compared to 2009. This reduction reached even higher percentages (greater than 50%) during September of 2010, when compared with September of 2009.
The samples from the river running through the studied area were very limited. However, significant pollutant levels were observed only at the site situated outside the pilot area, on the upper reaches of the river. Judging from the detected pollutant levels at this site, and from the fact that the pollutants were not detected in the other river samples, it is suggested that was either a point source pollution stemming from poor practices, or an unrelated coincidence.
In the assessment of pollution in leachates from the unsaturated zone, it is more accurate to use the total quantity of pollutants, rather than the concentrations. This is because the water quantity collected every time depended directly on precipitation and irrigation, and therefore fluctuated greatly, directly affecting the pollutant concentrations in the sample. From the total pollutant quantities detected in the water samples of the unsaturated zone, a reduction of approximately 47-50% was calculated, during 2010 compared to 2009. Analytically, the percentage reduction of herbicides reached 51.5% (comparing July 2010 with July 2009).
However, a significant increase was observed in the concentrations of insecticides (imidacloprid, azinfos-ethyl) during 2010, when compared with 2009. This increase represents very low absolute values, and was entirely explicable and anticipated due to entomological problems in the area, which corresponded to the recorded inputs in the area (Action 3).
The total concentrations of pesticide residues in the soil samples were reduced by 50% during September and 73% during July, of 2010 compared to the respective months of 2009.
Overall comparison of bioassays in aquatic organisms and all samples types revealed that toxicity was significantly reduced between 2010 and 2009. The exceptions were the samples of the unsaturated zone, in which toxicity showed an increasing trend during September 2010 compared with September 2009, despite the overall reduction in pollutant levels. This result can be put down to the increase in insecticide levels. These are especially toxic for aquatic organisms (and particularly for Daphnia magna), and represents a qualitative risk increase, despite the quantitative reduction.